Phosphorylase kinase is a hexadecameric oligomer of four dissimilar subunits with the stoichiometry (` k)4. The molecule is a bilobal bridged structure rather like a butterfly. Monoclonal antibodies are being raised to the individual subunits. The anti-alpha antibody was labeled with Au11 and clearly showed the C-terminal epitope from the alpha subunit to be located at the four wingtips of the butterfly-like kinase structure. Recently, the anti-beta Fab' was labeled with Au1.4nm as was the anti-gamma Fab'. Studies are in progress to localize these two subunits in the PK molecule.